the soy situation {guest post}

the soy situation // www.heynutritionlady.comA few years ago I had the privilege of meeting the wonderful Kellie of Food to Glow at a food blogger conference. We had an instant connection and a lot in common – Kellie is a cancer nutrition educator – and over the years it has seemed that we might in fact share a brain; it happens more often than not that we post an almost identical recipe within a day or two of one another, without ever having discussed it first.

I get a lot of questions about the soy situation, and while my answer is based on a good amount of scientific nutrition education, I’m no expert in this department. A while back, after a reader emailed me asking about soy milk, I turned to Kellie for more clear guidance because, although she’s about to claim that she’s not an expert, in my opinion she definitely is. That thoughtful and thorough email lead me to ask her if she’d consider writing a guest post on the subject, and thankfully she has managed to squeeze us into her busy schedule. So, without further adieu, the lovely Kellie with some words on The Soy Situation:


Disclaimer: I am not an expert on soy. Or, in fact, an expert on anything. I do however see many people who are being treated for breast cancer in my work as a cancer health educator with a major UK cancer charity. And one of their main questions is “should I be eating soy?”

Katie has kindly asked me to go through this highly controversial subject with you, but please know that the picture on soy is developing all of the time. I tend to walk the moderation-in-all-things line, but there will be some people who should be especially cautious about soy: those with thyroid problems or allergies, or those who have issues with nutrient absorption. In the main this piece focuses on hormone-related cancers, and soy’s effect – or not – on risk. This is not a definitive article by any means and should not be seen as such. But I hope that you find it interesting nonetheless.

spicy tofu dan dan noodles from

Spicy Tofu and Vegetable Dan Dan Noodles from Food to Glow

Pick up a protein bar, a store-bought cake, a can of soup, a tub of ice cream, a loaf of bread, a pack of sausages, a veggie meal. Read the label. What do they all have in common? Soy.

Found in approximately 60% of manufactured foods soy has – in the past 40 or so years – transformed from an exotic, whole food ingredient found almost exclusively in the Far East, to one that is highly-processed and present in thousands of commonly available foods. It is used in many foods as a cheap filler and to help extend a product’s shelf-life. It is also, in the US at least, highly likely to be a GMO food unless organic.

But does that make soy bad? Does that make soy inherently unhealthy? Does soy have anything positive to add to our diet and health? The answers thus far are not at all clear. But here is a bit of what we know, and why we should care.

turmeric tofu scramble // the muffin myth

Turmeric Tofu Scramble 

Over the years, soy has gone through more image changes than Madonna. Seen for years as a healthful food – a viable, protein-rich alternative to red meat – more recently soy foods have been said by some ‘health experts’ (I’m not meaning to be flippant, but really no one is a health expert) to lower testosterone levels in men, hamper thyroid function, reduce cognitive function, and block nutrient absorption. Most of these points can be refuted upon closer inspection, for example, soaking and fermenting soy minimises the phytic acid in it, an acid that interferes with iron and zinc absorption. Eating sensible rather than heroic amounts of soy also gets around many of the potential problems.

Here is where it all gets a bit tricky. Why? Because this innocuous looking seed/pea– Glycine max. – has been eaten for thousands of years in China and Japan, and is seen in those countries as integral to health.

Numerous large clinical studies suggest that people who regularly eat soy foods, such as people in Asia, have reduced menopausal symptoms, lower risk of heart disease and less osteoporosis. Some research has also found that eating soy foods can help prevent hormone-related cancers, such as breast, aggressive forms of prostate, and uterine cancer. And it is on the subject of cancer where the controversy really kicks in.

japanese breakfast skillet from

Japanese Breakfast Skillet with tomato, ginger, and miso sauce from Food to Glow

So, does soy help prevent cancer, or can it in fact cause cancer?

To get to the heart of this it is important to know what are the active compounds in soy, the stuff that cause changes in the body. You may already be aware that soy contains phytoestrogens, which are plant chemicals that chemically resemble estrogens – the sex hormones made by our bodies. Phytoestrogens are found in many plant foods, but soy has by far the highest concentration. Phytoestrogens contain particularly active compounds called isoflavones. These are often the ones you see listed in women’s health supplements. These are compounds that some women use as a natural alternative to hormone replacement therapy in order to dampen down distressing menopausal symptoms.

Eating modest amounts of soy has an equilibrating effect – increasing estrogen levels when they are low, and reducing them when they were too high. Studies (both animal and human) have shown that it has an anti-estrogenic effect on body cells that have estrogen receptors. The basic anti-cancer theory is that because phytoestrogens/isoflavones are a weak estrogen they bind to the receptor sites on relevant cells and lock out circulating – and stimulating – human estrogen. This is important because too much estrogen (particularly, estradiol) can promote the growth of (but not cause) cancer. This action is what is thought to be what is so protective about soy, and may be one reason why Asian women are less prone to breast cancer than Western women.

baked sriracha tempeh bowls // the muffin myth

Baked Sriracha Tempeh Bowls

But here’s the catch. Most of the robust, large studies are of women in China and Japan. And they eat the ‘good stuff.’ Not for them the fake hotdogs, soy chunks, soy margarines, milks and yogurts. No, soy is eaten primarily as tofu, and as the fermented foods tempeh, miso and natto.

A very different ‘beast’ altogether.

Additionally, the traditional diets of women in east Asia are also much richer in plant foods generally, sea vegetables (e.g. wakame, nori), fish, nutrient-rich broths, and they have less meat, much less dairy, typically weigh less, drink less alcohol, and exercise more. In studies of soy’s effect on health it is very difficult to filter out the effects of these other factors, so whether their lower breast cancer incidence is due to soy consumption or other dietary and lifestyle factors is unclear.

Crucially perhaps for the outcome of some of the studies, soy in these traditional forms is eaten from a very young age – pre-pubescently. Research indicates that soy eaten in the early years may give the most anti-cancer effects later in life. Protecting breast, prostate and uterine cells in the growing years is seen as one key to either preventing cancer, or – in the case of prostate cancer – reducing its most aggressive forms. Once women reach the age of menopause, introduction of soy may have less effect. Men’s response to soy seems to be less influenced by age of introduction as its action may be more to do with nipping cancer in the bud once it is present (even at pre-clinical stages) by influencing programmed cell death (apoptosis).

coconut lemongrass tofu soup from

Coconut and Lemongrass Tofu Soup from Food to Glow

Other ways soy may help prevent cancer generally is through antioxidant defense, DNA repair, inhibition of cancer growth (angiogenesis), and spread of cancer to other sites in the body (metastasis). Interestingly, when women from the Far East move to western countries and adopt the local diet and lifestyle (typically meatier and with less vegetables and fruits; more sedentary) their risk of cancer tends to increase. This is one of the strongest indicators that it is overall lifestyle factors rather one single component that is protective.

There is some scientific disagreement over whether soy is safe for those who have had breast cancer. Two recent US studies that followed just over 4500 women post-breast cancer diagnosis and treatment for seven years showed that those who got the most isoflavones from soy foods had a 24 percent lower risk of recurrence than those with the least. Other studies have shown that phytoestrogens may promote cancer recurrence (possibly because even weak amounts of breast cell stimulation after the menopause – when estrogen is meant to be low – is unhelpful). Still others show no effect either way.

Because the evidence is mixed and research is ongoing, many doctors recommend that women undergoing hormonal therapy or who have estrogen-receptor-positive breast cancer avoid soy supplements because they contain high concentrations of isoflavones. (I would certainly agree.) However, small quantities (one serving a day) of soy foods as part of a varied and mixed diet are currently regarded as safe by most doctors. If you are being treated for breast cancer, do ask your doctor for advice.

sunshine sauce with steamed edamame and veg // the muffin myth

Orange Carrot Miso Sunshine Sauce with Steamed Edamame and Veg

The Bottom Line

Regardless of potential cancer risk and risk reduction it seems sensible that if one eats soy to choose the least processed forms – tofu, tempeh, miso and natto – and minimize the fake meat and soy milks; which are often artificially flavoured, sweetened, full of sodium and contain lowest quality soy. Organic brands are also advised.

And, coming full circle, moderation in all things. Just because a little might be good, it doesn’t necessarily follow that more is better. In food and nutrition, the opposite is often the case. Widen your diet to include a variety of colourful plant foods – including nuts, seeds, whole grains, vegetable, fruits, herbs and spices, and other beans and legumes too. For a variety of reasons a balanced, plant-based diet is widely held to be protective against cancer and many other diseases. But you already knew that, didn’t you?

Further reading:

And a very interesting overview and sarky piece of writing from – of all places – the gourmet’s mag of choice, Bon Appetit:

Find more of Kellie’s work on Nutrition and Cancer on Food to Glow.







    • Katie Trant says

      Hi Tracy! I’d be happy for you to post a teaser with a link back to the original post, much as you have with the neck pain post on your blog. Thanks for asking!

  1. Monica Shaw says

    Extraordinarily interesting. When I lived in the States I was totally smitten with “Boca burgers” and “Boca sausages”. Let’s face it, I’d probably still really enjoy them if I ate one now. But I’ve since become wiser to the ways of soy and now stick mainly to tempeh. I’m trying to incorporate more miso into my diet, not so much for its health benefits but because it tastes nice and it seems like foods that involve miso always leave me feeling awesome! Anyway, good to see both sides of the story presented here. Thank you!

    • Katie Trant says

      I also used to dig those soy meat products, and from time to time I’ll still indulge in a wee bit of vegetarian pizza pepperoni (cause if I was eating regular pepperoni it’d be pretty processed too, right?) but now I mostly stick to tempeh, tofu, miso, and edamame. I also love the way miso dishes make me feel! Thanks for stopping by, Monica!

  2. Of Goats and Greens says

    Wonderful post. I won’t eat soy that is manipulated into being something else, but I do enjoy miso soup, age dashi tofu, and that tempeh which has been made without wheat. It is also fermented. Thanks for this great post, things to think upon!

  3. kellie@foodtoglow says

    Thanks Katie for the opportunity to share this important topic with your readers. I am so pleased that it seems to have been not only of interest to your readers (it is an issue for us all, I think) but have been kind enough to leave such lovely comments. It was my pleasure to guest post for The Muffin Myth. Just to say to your readers that I have other cancer-related issues covered under my cancer and nutrition tab on my blog, food to glow.

    • Katie Trant says

      Thank YOU Kellie for the fabulous article. It’s clearly struck a chord with many of my readers! I’ll link to your cancer and nutrition tab from the article so that others may find it easily.

  4. SweetonGreens says

    Great article! I think it’s really great that you drew in the importance of the diet as a whole and what form soy is being consumed in depending on the culture. Very well written and informative- thanks!

  5. Lisa says

    Fantastic article. Well-researched, clearly argued, concise. Tallies with what we at Divine Vegan have been teaching. Will share with our followers. Thanks so much!

  6. Cate says

    I appreciate your words, a well considered article, I have an underactive thyroid (long term problem for which the symptoms do not abate even when my levels are in a decent range). I find too much soy IN things is worse than a tofu stirfry. For me, it’s the hidden soy that’s the problem.

  7. The Savvy Sister says

    Soy is a tough on isn’t it? Bravo for tackling this controversial issue (wars have been fought over it LOL)
    I love that you say in so many words that soy isn’t the sum of your whole diet…TRUE!
    As a breast cancer survivor and health and wellness advocate I can tell you without a doubt that eating fermented soy is the best thing you can do to prevent cancer AND BREAST CANCER RECURRENCE. The trick is to eat 1-2 servings ONLY and avoid soy protein isolates found in processed foods. In the studies that showed soy increased cancer risk, soy protein isolates were used….isolates are fractionated soy protein…VERY DIFFERENT from whole and fermented forms of soy.

    It is also very important that organic soy is consumed as I know in the US, over 95% of soy is GMO, which opens up a whole other can of worms.

    I hope you don’t mind that I include this link for any breast cancer survivors out there.. (no problem if you don’t want links in your comments, and you can delete this comment from the stream)

  8. Jeanne @ Cooksister says

    What a great piece! Kellie is an expert, whatever she tells you 😉 What annoys me about all these stories on a particular single food being good or bad is exactly what you explain in your article – it’s not one food, it is the entire lifestyle context within which that food is eaten! There is no magic bullet, people…

  9. Shannon says

    Thank you so much for this post, you really hit the nail not the head with this one. I love reading Kellie’s blog Food to Glow but this is the first time I’ve been to your site and it’s incredible. Thank you Kellie for your amazing insight and all the helpful links.

    • Katie Trant says

      Welcome to The Muffin Myth, Shannon! I’m so glad you’re here 🙂 And yes, Kellie’s brilliant post sheds much needed light on a tricky subject. Glad you found it helpful.

  10. Cassie says

    Thank you for this post! I totally relate to the soy controversy! I love my tofu but the whole soy incident makes me scared! It’s all about moderation for me, none of that weird soy tofurky or whatever 😛

    • Katie Trant says

      I used to love soy ‘meats’ and ate a lot of them for a while, but when I started studying nutrition and food systems my definition of what ‘real’ food is thankfully evolved, and I now eschew fake meats for the most part. The one exception I make is vegetarian pizza pepperoni once every six months or so, and I rationalize it by telling myself that if I was a meat eater the pepperoni would also be quite processed. For the most part it’s just organic tofu and tempeh for me!

  11. Apsara says

    Thank you for this lovely article. This is the best write-up I have seen for the controversial soy. This has made me clear many of the questions I’ve had.

  12. Alissa says

    Thank you for this! For most of my life as a vegetarian, soy has been one of my main sources of protein, and I eat it a few times a week. I’ve been a bit concerned with all of the recent controversy surrounding it, but really, with so many different viewpoints, I didn’t know what to make of it. I definitely agree with your “moderation in all things” viewpoint, and feel a bit better now about the fact that most of the soy I consume is minimally processed.

    • Katie Trant says

      I also eat soy on an ongoing basis, always organic tofu or tempeh. It’s interesting that with life and nutrition we keep coming back to this moderation thing. It’s so simple, yet something so few people practice.

  13. Linda @ Veganosity says

    I’m standing up and applauding! This is an excellent and balanced article. I actually asked my Ob/Gyn about soy consumption when I became a vegan and he said that there is no proof that soy causes cancer, only a slight correlation. He also said that studies of women who moved from Asia to the U.S. showed an increase in cancer, leading him to believe that a diet based on highly processed food is much more suspicious than eating soy. Our conversation was in depth and your article confirms what he told me. I’m going to share this with my readers. Thank you!

  14. Rhonda says

    Thanks. I listen to different podcasts and hear “no soy” then “eat soy” then “no soy”. Nobody ever tells me why – although there is sometimes a little fear mongering… “No soy….cancer…” This is helpful information which explains in clear english some of the key factors. I specifically appreciate the comments regarding the different types/sources of soy. That was really clarifying and rings true with my understanding of nutrition in general. Didn’t know I wanted information on this so thanks for delivering me something I needed and didn’t even know it!!

    • Katie Trant says

      Glad you enjoyed the post, Rhonda. What nutrition podcasts are you listening to? I enjoy a good podcast, but haven’t found any nutrition related ones that really speak to me.


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